import multiprocessing.pool as mpp


def istarmap(self, func, iterable, chunksize=1):
    """starmap-version of imap
    """
    if self._state != mpp.RUN:
        raise ValueError("Pool not running")

    if chunksize < 1:
        raise ValueError(
            "Chunksize must be 1+, not {0:n}".format(
                chunksize))

    task_batches = mpp.Pool._get_tasks(func, iterable, chunksize)
    result = mpp.IMapIterator(self._cache)
    self._taskqueue.put(
        (
            self._guarded_task_generation(result._job,
                                          mpp.starmapstar,
                                          task_batches),
            result._set_length
        ))
    return (item for chunk in result for item in chunk)


# if python 3.8+
# def istarmap(self, func, iterable, chunksize=1):
#     """starmap-version of imap
#     """
#     self._check_running()
#     if chunksize < 1:
#         raise ValueError(
#             "Chunksize must be 1+, not {0:n}".format(
#                 chunksize))

#     task_batches = mpp.Pool._get_tasks(func, iterable, chunksize)
#     result = mpp.IMapIterator(self)
#     self._taskqueue.put(
#         (
#             self._guarded_task_generation(result._job,
#                                           mpp.starmapstar,
#                                           task_batches),
#             result._set_length
#         ))
#     return (item for chunk in result for item in chunk)


mpp.Pool.istarmap = istarmap